1. Field of the Invention
This invention relates to an insulation displacement contact (IDC) terminal with improved contacting characteristics.
2. Description of the Prior Art
Typical prior art IDC terminals include at least one pair of opposing legs extending upward from a base section in order to define a U-shaped structure wherein the opening is for receiving a wire-type conductor so that an electrical interconnection may be established. As the wire-type conductors typically include a conductor surrounded by a protective insulating cover, in order to effect connection with the conductor it is necessary to expose a portion of the conductor to which the electrical contact may be established. In order to separate the insulation, a cutting surface is included along at least one of the legs that is inwardly directed to be in an opposing relation with the other leg. Typically, cutting surfaces are provided on each leg with the cutting surfaces being positioned in a corresponding and opposing manner to each other. The cutting surface parts the insulation as the conductor is pressed into the opening of the U-shaped slot. Subsequent the cutting surfaces, along the legs are contact surfaces that engage the conductor so that after the insulation is displaced, further insertion of the wire results in an electrical connection being established. IDC construction of this type is well known in the industry and performs satisfactorily in a wide range of applications.
However, a problem with this construction is that the combination of the U-shaped IDC slot and the necessity of slicing through the insulation prior to seating the conductor in engagement with the contact surfaces, inherently produces a structure where the cutting surfaces will be deflected further apart in response to the insertion of the conductor. As the cutting surfaces need to be located towards the free ends of the legs so that the insulation can be cut as the wire is initially seated in the opening and the contact surfaces are located near the base where the legs are joined to the base so that the contact surfaces engage the conductor after the insulation is cut, the cutting surfaces undergo greater resilient displacement and offer less normal forces than the contact surfaces. In addition, cutting through the insulation requires more force than contacting the conductor so that the greatest force is exerted at the extreme ends of the legs.
When the arms are designed to provide adequate strength for cutting the insulation, it is not uncommon for there to be little resiliency at the contacting locations. In these instances the electrical interconnection may be susceptible to failure because any external forces exerted at the interconnection will tend to displace the conductor and, as there is little resiliency available, small displacements cannot be accommodated. If the arms are constructed to provide the proper resiliency at the contact surfaces, most likely, the strength at the cutting surfaces will be insufficient to assure reliable cutting of the insulation.
Therefore, the prior art IDC terminals of this type may have cutting surfaces that are susceptible to separation as the wire is inserted into the opening, thereby only partially cutting through the insulation or the contact surfaces therebelow may have less resiliency than is necessary to form an effective and durable electrical connection. The normal process is to compromise and create a structure that tries to do both. In some cases this will be successful, especially where the size of the wire and its core are closely controlled. In other instances, it is known to provide a separate support member to provide extra stiffness to the legs at the cutting portion as the wire is being inserted into the slot to assure that proper cutting occurs. This support member may be included in the housing in which the IDC is disposed or be provided by the tooling used to push the wire into the opening. In some applications neither of these solutions is possible or it may be necessary to be able to accommodate a range of possible wire sizes.